Northern shrikes, Lanius excubitor (the butcher watchman), are predatory songbirds, that behave much like a hawks or falcons. Like other raptors, shrikes have very good eyesight, heavy large heads, hooked bills and a notch (tomial tooth) in the beak, which is thought to be used to dislocate the neck of vertebrates (Sloane, 1991). But, unlike raptors, shrikes do not have heavy talons, which they compensate for by using their environment. Shrikes are thus known best for their behaviour of impaling their prey on sharp objects, such as thorns, spines or barbed wire, from where they can better manipulate and tear at their prey (Yosef and Pinshow, 1989). Sometimes the shrikes won’t consume their prey right away, caching them for later and using them as larder (Yosef and Pinshow, 1989).

Impaling prey also allows northern shrikes to eat prey that contain deadly toxins such as insects and amphibians (Antczak, et al., 2005). They let the toxins breakdown in their prey for several days before consuming them (NatGeo). Shrikes have adapted to deal with the toxins within the skin of amphibians by skinning them before consumprion, which is facilitated by having the prey impaled (Antczak, et al., 2005).

Short video of the impaling behaviour of shrikes by National Geographic Wild.

Another reason for impaling their prey is for mate selection. This was hypothesized by Yosef and Pinshow due to the lack of observed caching behaviour in female northern shrikes – only males seemed to do it (1989). In their studies, Yosef and Pinshow found that male northern shrikes with larger caches of prey (an indication of higher quality males) were indeed much more successful in acquiring a mate (1989). However, males (who are socially monogamous) have been seen to also cheat on their mates with extra-pair females. A male’s reproductive success (i.e. number of fertile offspring) is limited by the number of females he copulates with, which thus leads them to try and get as many females as possible (Tryjanowski and Hromada, 2005). They do this by presenting the extra-pair females with prey in more secluded areas, away from their social mate (Tryjanowski et al., 2006). It was found that the males would present prey with much higher energy value to the extra-pair female than to the social mate in order to entice them away from their respective social mate (Tryjanowski and Hromada, 2005). Interestingly, as a result of their increased experience of impaling prey (from showing off to the ladies), it has been found that male northern shrikes show much better skills at impaling their prey than females (Antczak, et al., 2012).

Literature Cited

Antczak, M., M. Hromada and P. Tryjanowski. 2005. Frogs and toads in the food of the Great Grey Shriken (Lanius excubitor): larders and skinning as two ways to consume dangerous prey. Anim. Biol. 55: 227-233.

Antczak, M., M. Hromada and P. Tryjanowski. 2012. Sex differences in impaling behaviour of Great Grey Shrike Lanius excubitor: Do males have better impaling skills than females? Behav. Proc. 91: 50-53

Nat Geo Wild. 2013. Butchering bird. National Geographic. Retrieved October 30, 2015,  https://www.youtube.com/watch?v=okQYO10MT3c

Sloane, S.A., 1991. The shrike’s display advertising. Nat. Hist. 6: 32–39

Spiczka, S. 2012. The frog in the apple tree. Retrieved October 31, 2015, http://sculptorsam.com/the-frog-in-the-apple-tree/

Tryjanowski P. and M. Hromada. 2005. Do males of the great grey shrike, Lanius excubitor, trade food for extrapair copulations? Anim. Behav. 69: 529-533.

Tryjanowski P., M Antczak and M. Hromada. 2006. More secluded places for extra-pair copulations in the great grey shrike Lanius excubitor. Behav. 144: 23-31

Vermeersch, G. 2011. unique impaling behaviour of shrikes. Retrieved October 31, 2015, http://mudfooted.com/unique-feeding-impaling-bird-shrike/

Yosef, R. and B. Pinshow. 1989. Cache size in shrikes influences female mate choice and reproductive success. Auk 106: 418–421.